I'm sure there is lots of digital circuitry within the box. Digital
circuitry = RFI ! ! ! I'd suggest temporily disconnecting the battery.
Let ADT know before you do so or they may interpret that as in ingress.
Also disconnect their dable, if any. I'll be with those two actions, the
RFI will cease.
Have you "sniffed" the ADT box and installation with a spectrum analyzer
and a small (maybe 5-cm in diameter or so) loop?
Dave - WØLEV
On Mon, Feb 16, 2026 at 8:26 PM Joseph Bouchard <joek1vw@gmail.com> wrote:
> Hi,
>
> We have a club station at a museum and are chasing down RFI (KB1BSM). I
> threw every breaker in the building with someone watching the panadapter.
> It didn’t kill the particular noise we are chasing, which shows an S9
> harmonic about every 34khz on 20m.
>
> Then someone said “we have an ADT security system with its own battery
> backup.” They think they can call ADT and get them to remotely shut it down
> temporarily for a test, but I’m a little skeptical… if they are talking to
> it remotely, it’s not really dead is it? I tried to get a model number but
> all I see is a red metal lock box with a little ground plane antenna, about
> 6” tall. I suspect it’s a cellphone antenna. I don’t expect that UHF
> radio is causing us problems on HF, but the system of sensor could be noisy.
>
> Anyway, my question for the group, are ADT security systems a known
> culprit for RFI?
>
> Thank you,
> Joe K1VW
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--
*Dave - WØLEV*
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